A roughness probe for the optical measurement of the roughness of surfaces with a reflection dispersion lobe has a measuring head 26 with an opto-transmitter and a plurality of opto-receivers. The opto-receivers 11, 12, 12' are connected to an evaluation electronic system 13 containing a quotient-forming stage 14. Said system forms the quotient of linear combinations of the received signals of the opto-receivers of two different combinations of opto-receivers. An output signal representative of the roughness of the surface 34 is produced on a display device 37. <IMAGE>
